10BASE-T wiring parameters. Unlike earlier Ethernet standards such as 10BASE5 and 10BASE2, 10BASE-T
does not specify the exact type of wiring to be used. This was done in anticipation of using 10BASE-T in
existing twisted pair wiring systems that may not conform to any specified wiring standard.
Instead, 10BASE-T wiring is specified using a set of characteristics that a 10BASE-T link
segment must conform to.
These include attenuation, characteristic impedance, timing jitter, propagation delay,
and several types of noise.
Wikipedia http://en.wikipedia.org/wiki/10BASE-T.